Electrical wiring systems employ a variety of connection means, for example, wire binding screw terminals, wire nuts, pressure-wire terminals, insulation displacement terminals, insulation piercing terminals, and push-in terminals. These types of connections are used in a variety of ways to permanently connect wires to electrical devices and terminal strips, as well as to make direct wire-to-wire connections.
However, for various reasons, some electrical connections are faulty or incomplete. For instance, electrical connections can loosen over time, and in some cases connections are loose due to improper installation or because they were otherwise improperly made. Also, connections that rely on screws (i.e., to fasten one conductor directly to another) can loosen due to vibration. As well, connections to ductile conductors like aluminium can loosen through deformation of the conductors. In addition, loose connections in series with medium to large loads sometimes result in small arcs that, over time, degrade already loose contact surfaces through pitting and burning.
Accordingly, loose connections can be poor electrical conductors, i.e., they can create high resistance junctions. These connections can heat excessively with high electrical current passing through the junction.
As is well known by fire investigators, high resistance connections cause fires. For example, with a 10 Amp load (not unusual in residential wiring systems), a 1 Ohm resistive connection must dissipate 100 Watts, and a 2 Ohm resistive connection must dissipate 200 Watts. It has been demonstrated that resistive connections can glow red-hot with normal household loads.
As is also known, the current that flows when a short circuit occurs is related to the impedance of the circuit. It is also known that circuit breakers of the type employed to protect branch circuits are designed to respond virtually instantaneously to short circuit conditions, and much more slowly to moderate overcurrent conditions. With unusually high circuit impedance from resistive connections, excessive wire length, and/or a large number of connections, the current that flows in a short circuit can be significantly reduced. This can have an adverse effect on the instantaneous tripping characteristics of circuit breakers, even to the point where the instantaneous tripping capability is ineffective in a short circuit condition.
Symptoms of Resistive Fault Conditions
The following are some typical symptoms of resistive fault conditions.                Reduced line voltage on circuits beyond the resistive connection. Voltage drop can be as little as a few volts when a fire hazard exists. This voltage drop is easily masked by variations in normal line voltage. Significant voltage drops can cause the line voltage to fall below normal limits.        Line voltage fluctuations with changing loads on circuit extremities beyond the resistive connection. The voltage drop (and heat) associated with a resistive connection is directly related to the current flow.        Increased heat at an electrical box containing a resistive connection. Electrical wiring and devices generate heat under normal conditions. Resistive connections are unique in that the heat is concentrated in a small area within the electrical box, but this can be masked by normal heating that occurs with large load currents.Safety Hazards of Resistive Fault Conditions        
The following are some safety hazards resulting from resistive fault conditions.                The primary hazard is fire caused directly by ignition of flammable materials close to the resistive connection.        Resistive connections can melt plastics and degrade insulation, creating a shock hazard.        
Currently, the common way to detect loose connections resulting in resistive fault conditions is to disassemble and examine each permanent connection in an electrical system.